SimpleTypeDeclaration:
    'simpleType' name=Name ':' primitiveType=PrimitiveType ('[' length=INT ']')?
 ;

// (A) this would store zero to length:
simpleType myTypeA : char

// (B) this would also store zero to length:
simpleType myTypeB : char[0]

// (C) this would store one to length:
simpleType myTypeC : char[1]

// (D) this would be illegal:
simpleType myTypeD : char[-1]

terminal MY_INT returns ecore::EInt: ('0'..'9')+; // <== can I write something to default to -1 for the EInt here?

SimpleTypeDeclaration:
    'simpleType' name=Name ':' primitiveType=PrimitiveType lengthModifiers=LengthModifiers?;
// now I can do a null check on lengthModifiers EAttribute to discriminate between (A) and (B)

LengthModifiers:
    '[' length=INT ']';

OptionalInt returns ecore::EIntegerObject: INT;

Dimension: '[' length=OptionalInt ']';

SimpleTypeDeclaration: 'simpleType' name=Name ':' primitiveType=PrimitiveType (dimensions+=Dimension)?;